Wiring devices, e.g., switches, receptacles, ground fault interrupting receptacles, dimming switches and certain communications and data disconnects are conventionally mounted by screws in outlet or switch boxes of the type describe in NEMA Standards OS-1 and OS-2. A cover plate is also mounted by screws to the wiring device to completely enclose the wiring and terminations. The standards for mounting the cover plate are described in NEMA Standards WD-1 and WD-6.
Conventional cover plate installations suffer numerous disadvantages. Since the outlet box can be recessed behind the wall surface by as much as one-quarter inch and the opening formed in the wall may only roughly conform to the height and width of the outlet box, the mounting strap for the electrical device may have only a limited "footprint" or contact area with the wall to align and position the electrical device. When insufficient contact area exists between the mounting strap and the wall adjacent the rough cut opening, the positioning of the mounting strap must be adjusted by the use of shims between the device and the box or the device must be only loosely mounted in the box. Loosely mounted devices or the use of such shims can adversely effect the grounding path of the device creating a safety hazard.
The cover plate is normally intended to complete the enclosure of the wiring and terminations with the outlet box by closing the open side of the outlet box. If the exposed cover plate must satisfy electrical enclosure standards regarding flammability and mechanical strength, the material and asthetic design of the cover plate can be severely limited.
Conventional mounting straps for wiring devices have oblong, oversized mounting holes to permit adjustment of the device within the outlet box. If a plurality of devices are to be mounted and covered by a single cover plate, the vertical and horizontal axes must be properly oriented to be received within the multiple openings in the single cover plate. This presently can be accomplished only by employing the cover plate as a template using a pointed tool while the devices are loosely mounted in the outlet box or boxes.
The conventional use of screws to mount the cover plate on the electrical device or its mounting strap detracts from the aesthetic appearance of the cover plate. Moreover, the metal screws must be conductively bonded to the grounding path.
Although cover plate mounting arrangements without screws have been disclosed, such arrangements have not been found to be effective. Typical examples are disclosed in U.S. Pat. Nos. 1,840,582 to Hubbell, 2,043,865 to Place, 2,740,873 to Cronk, 3,011,008 to Slater, 3,197,549 to Good, 3,518,356 to Friedman, 3,987,928 to Mori, and 4,500,746 to Meehan.